The invention relates to a rotary actuator comprising a first rotatable part, having a control surface with an undulating or sawtooth profile, and a fixed second part, having at least one detent element running on the control surface.
Rotary actuators of this kind are used in motor vehicles, for example, and are used to control different functions, which are indicated on a display, for example. They can be used to control different systems in the motor vehicle, such as a navigation system, an integrated telephone, an infotainment system and the like, and also to control or choose individual functions within the systems. A rotary actuator of this kind often also has a selecting function, being capable of axial actuation to select a desired function, thus having an axial switching function. However, the use of a latched rotary actuator of this kind is not restricted exclusively to the motor vehicle sector; on the contrary, a latched incremental rotary actuator of this kind can, of course, also be employed on any other equipment.
In order to provide the large number of functions and settings of many different kinds by the rotary actuator in a way which is recognizable for the user, it is necessary to provide unambiguous feedback in the form of haptic and acoustic feedback by the movement of the rotary actuator alone, thus ensuring that, as the rotary actuator is moved, the user “experiences” each individual movement from one latched position into the next both haptically and acoustically. For this purpose, the rotary actuator has a first rotatable part, which the user actively moves, which has a control surface with an undulating or sawtooth profile. This surface interacts with a detent element running on the control surface, which is provided on a fixed second part, relative to which the first part is moved. On known rotary actuators, the detent element is generally designed as a leaf spring component with a detent nose facing the control surface, the usual practice being to provide two detent elements of this kind, generally arranged offset by 180°, which are either fixed without play or mounted with a slight play. As the rotatable part is turned, the detent nose of the detent element runs up the control surface and is moved out of the detent receptacle by the control surface projection. As it is turned further, the detent nose reaches the tooth head of the control surface. If it is turned further once again, the detent nose of the spring fixed without play slides down the opposite tooth flank and enters the detent receptacle without the occurrence of a jump. However, if the detent nose of a spring subject to play reaches the tooth head and passes beyond it, it is displaced abruptly into the detent receptacle of the control surface and strikes against the opposite stop or opposite tooth flank, and there is a clicking noise. In the case of detent elements fixed without play, however, the clicking noise, in particular the intensity thereof, is dependent on the speed of operation. If the user turns the first part very slowly, there is as it were a “damped” slow sliding motion of the detent element into the latched position and consequently a slight clicking noise, in contrast with a rapid rotation, in which case the detent nose snaps very quickly and heavily into the detent receptacle. In the case of detent elements of this kind, which are guided without play, the acoustic behavior is therefore not constant irrespective of the rotation of the first part. On the other hand, a very slight rotational play in the notch is achieved. When the detent elements are mounted in a manner subject to play, acoustics independent of the speed of operation and hence more constant acoustic behavior are produced, but the rotational play in the notch increases, thereby impairing the haptic properties. This is because the snap action, in particular, contributes to the haptics and, as described, the snap action is ultimately dependent on the speed of operation. That is to say that both the haptics and the acoustics vary depending on the mounting of the detent elements and the speed of operation and that therefore a constant level of convenience of operation and uniform feedback to the user are not achieved.